These are the extra dependencies such as CSS or JavaScript that the xblock needs to render itself. They are hashed so that the JavaScript logic can decide if the dependency has already been injected into the page.

My change split the logic for handling the preview rendering from the editor rendering. For both the unit page and the container page we render the preview, so that's the code here. In the 'else' clause below, the editor is rendered, and only in that case are the editor fragments added.

Make sense? Is there a way to make the code read more clearly?